Two-way digital wireless communication systems that are coupled to the public switched telephone network (PSTN) are well known. An example is the S35XGB1602AP telepoint base station used with the S35XCD1000AA personal telephone, both manufactured by Motorola, Inc. of Schaumburg, Ill. That system typically comprises a plurality of the telepoint base stations at a plurality of telepoint sites. A transceiver in the telepoint base station communicates with a personal telephone by means of a well-known synchronous, time-division-duplex (TDD) communication protocol referred to as the CT2 protocol. The CT2 protocol specifies a TDD timing such that the base station and the personal telephone must alternately transmit for one-millisecond and then receive for one millisecond. For further information on the CT2 protocol one is referred to "CT2 Common Air Interface," Version 1.1, document number IETS 300 131:1990, published 30th Jun., 1991, by the European Telecommunications Standards Institute (ETSI), of Valbonne Cedex, France.
A typical large city requires thousands of telepoint sites for good coverage. Because radio coverage of one site can overlap with the radio coverage of another site, it is preferable that the TDD communications of the sites be synchronized with one another for best performance. That is, it is preferable that all base station sites transmit simultaneously and receive simultaneously, else communication range becomes somewhat compromised due to mutual interference.
To synchronize the base stations a master timing signal is generated and typically is distributed over a wireline network to a synchronization port on the base station. Occasionally, a problem occurs somewhere in the system, causing loss of the master timing signal. When this happens, the TDD timing of each base station has to be generated internally, and the system is no longer synchronized. Unfortunately, when the master timing signal is later restored, a resultant sudden shift in timing signal edges can cause a loud audio noise burst in the conventional system. The loud audio noise burst is audible in both communication directions and has been a source of user complaints in existing CT2 systems.
Thus, what is needed is a method of preventing the audible noise burst that has typically occurred during restoration of an interrupted master timing signal in a CT2 system.